The advent of digital storage contributes significantly to the technical progress in the production technique of television programs. The DRAM, among different types of the digital storage, is gradually increasing in its storage capacity so that one scanning line, one field picture, one frame picture and even a sequence of plural pictures can be stored therein. The digital storage is economically practicable even in consideration of its production cost, circuit scale or power consumption. Among the instances of application of the digital storage, such as DRAM, there are so-called DME (digital multi-effects) used when modifying the picture to an optional shape or when moving the picture such as at the time of creation of television programs.
Meanwhile, when e.g., the conventional DME executes processing of interpolation of picture signals of the conventional HD (high definition) format, so-called four-point interpolation, which consists in calculating picture signals of a position for interpolation using picture signals corresponding to four pixels lying around the position for interpolation, is used. If the conventional DME execute processing of the interpolation on picture signals of the SD (standard definition) format, the processing of so-called 16-point interpolation is used, in which, after field/frame conversion, the number of horizontal scanning lines is doubled, and picture signals at the position of interpolation are calculated using picture signals corresponding to 16 pixels lying in the vicinity of the position of interpolation. If now the four-point interpolation is applied to picture signals of the SD format, the picture signals resulting from the interpolation are lower in quality than those obtained on 16-point interpolation. It is therefore desirable if, in implementing DME capable of processing picture signals of the HD format and those of the SD format, the four-point interpolation and the 16-point interpolation can be executed for picture signals of the SD format and those of the HD format, respectively. However, there lacks such DME in the current technical level.
Also, in the DME, it is practiced to interpolate picture signals at a certain position using picture signals of plural signals lying around the position, for example, four pixels lying at upper, lower, left and right positions. However, if the position desired for interpolation is near a picture edge, it may be an occurrence that no sufficient number of neighboring pixels is available. In such case, processing different from the usual interpolation is needed. That is, there is the necessity of verifying whether or not the processing of usual interpolation is applicable to the particular position for interpolation. Consequently, a dedicated circuit for making the decision in this respect is needed.
In the conventional DME, it is also practiced to interpolate picture signals of a preset position with picture signals of pixels lying in the vicinity of the position. However, since the picture signals input to e.g., the DME are of the 4:2:2 (Y/U/Y) format, in which the positions of the chroma signals U, V associated with luminance signals Y are geometrically offset, there is raised a problem that a memory cannot be efficiently utilized. There is also an additional problem that, since the luminance signals Y and the chroma signals U, V are different in the spatial frequencies from each other, processing pertinent to color, such as colored spotlight effect or trailing effects accompanied with color changes, cannot be performed.
In the conventional DME, directed to the processing of the SD format picture signals, a field memory is used for changing the scanning direction from the horizontal direction to the vertical direction. However, if it is considered to process the picture signals of the HD (high definition) format, higher in resolution higher than the picture signals of the SD format, a larger storage capacity and a higher read-write speed, are required, thus raising a problem that the conventional field memory cannot be used.
On the other hand, if a general-purpose memory is usable in producing e.g., the DME, low cost can be achieved. However, in view of the limitations imposed on the sorts of the bit widths of the general-purpose memory, the bit width of input picture signals needs to be matched to the bit width of the general-purpose memory.